Having tried similar things, I cannot stress enough how much you want to be printing molds like this in TPU unless you really really want your mold to be permanently embedded in the concrete
You can also print the object and use it to make a silicone mold, right? That doesn’t stick to concrete.
@RegalPotoo @Wilshire good point. Release agents are used for casting concrete. They look to be oil and water mix so I’m guessing most plastics would be compatible.
Also has to be a clear path out for the print/concrete.